Salivary Sodium-Potassium Ratio and Plasma Renin Activity in Hypertension

Abstract

The cause of the suppression of plasma renin activity (PRA) in many patients with essential hypertension and normal aldosterone excretion is unknown. Since mineralocorticoid excess can lower PRA, we attempted to evaluate the activity of salt-retaining hormones in these patients by measuring the salivary Na/K ratio. The median Na/K ratio in 20 hypertensive patients with suppressed PRA and normal or low aldosterone excretion was 0.71. This was significantly lower than the median of 1.38 in 29 normal subjects and the median of 1.05 in 15 hypertensive patients with normal PRA. Excess dietary intake of salt is a possible cause of PRA suppression in these patients, but our findings indicate that high rather than low Na/K ratios would be expected if this were present. On the other hand, both the salivary electrolyte changes and the suppression of PRA are consistent with the hypothesis that mineralocorticoid excess is present in these patients, despite the failure to demonstrate elevated excretion of aldosterone.